OBJECTIVE: To understand the detailed biochemical structure and the mechanism of oncogenicity of RNA tumor viruses. APPROACH: (1) Phosphoproteins. The viral proteins are labeled with 32p. The phosphorylation patterns are studied in different virus strains. The functions of phosphoproteins are studied both in vitro and in vivo with respect to kinetics of phosphorylation of viral proteins. (2) Surface properties of the viruses. Isoelectric points of the whole virus and the individual glycoproteins are studied. The peptide maps and carbohydrate structure of glycoproteins from various virus strains are compared. (3) The RNA structure of xenotropic viruses is studied with respect to the RNase resistance and oligonucleotide fingerprinting.